Epoxides constitute an important class of -chemical intermediates useful for the preparation of polyether polyols, glycols, glycol ethers, surfactants, functional fluids, fuel additives and the like. Many different methods for synthesizing epoxides from the corresponding olefins have been described in the literature. A Japanese patent application assigned to the Tosoh Corporation and published in 1992 (Kokai No. 4-352771) proposed making propylene oxide by reacting propylene, hydrogen and oxygen using a catalyst comprising a Group VIII noble metal and a crystalline titanosilicate. Improvements to or variations of this basic process were subsequently described in the following published patent applications: WO 97/25143, DE 19600709, WO 96/02323, WO 97/47386, WO 97/31711, JP H8-269030, and JP H8-269029.
As with any chemical process, it would be desirable to attain still further improvements in epoxidation methods of this type. In particular, increasing the ease of catalyst preparation and use would significantly enhance the commercial potential of such methods.
In the usual preparation of Group VIII metal modified zeolite catalysts, the Group VIII metal is added as a soluble compound solution to the solid zeolite particles and after an appropriate time the particles now containing the Group VIII metal are recovered, dried and calcined. Problems have existed as to the reproduceability of such procedures and the activity of the catalysts so-produced.